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Abstract:

In some embodiments of the present disclosure, a sensor comprises a
substrate, a sensor element and an energy-harvesting device. The sensor
element comprises a plate, and the plate is moveable with respect to the
substrate. The energy-harvesting device is formed on the plate of the
sensor element.

Claims:

1. A device comprising: a substrate; a sensor element connected to the
substrate and comprising a plate, the plate moveable with respect to the
substrate; and an energy-harvesting device, the energy-harvesting device
formed on the plate of the sensor element.

2. The device according to claim 1, the energy-harvesting device
comprising a coil formed on the plate.

3. The device according to claim 2, further comprising a permanent magnet
positioned to cause a magnetic field to pass through the coil.

4. The device according to claim 1, further comprising a controller,
adapted to use at least a portion of energy harvested by the energy
harvesting device to power the device.

5. The device according to claim 1, the energy-harvesting device adapted
to harvesting energy using a resonant mode of the plate.

6. The device according to claim 1, the sensor element being a magnetic
field sensor.

7. The device according to claim 6, the sensor element being a Lorentz
force magnetic field sensor with capacitive detection responsive to
motion of the plate.

8. The device according to claim 1, the sensor element being a motion
sensor.

9. The device according to claim 1, the sensor element being a motion
sensor with capacitive detection responsive to motion of the plate.

10. A system comprising: a substrate; a plate moveable with respect to
the substrate, the moveable plate adapted to move in response to an
environment variable; an energy harvesting device formed on the moveable
plate; and a controller adapted to power the sensor system using at least
a portion of energy harvested by the energy-harvesting device.

11. The system according to claim 10, the moveable plate formed on the
substrate and the controller formed on the same substrate.

12. The system according to claim 11, the moveable plate formed over the
controller.

13. The system according to claim 10, further comprising elastic
connections connecting the moveable plate to the substrate and the energy
harvesting device comprising a spiral coil formed on the moveable plate
connected to the controller via the elastic connections.

14. The system according to claim 13, further comprising a permanent
magnet positioned to cause a magnetic field to pass through the spiral
coil.

15. The system according to claim 10, the energy-harvesting device
adapted to harvest energy using a resonant mode of the moveable plate.

16. The system according to claim 10, further comprising electrodes for
capacitive detection responsive to a motion of the moveable plate.

17. The system according to claim 16, the moveable plate further
comprising a wire loop and forming a magnetic field sensor.

18. The system according to claim 16, the moveable plate further
comprising fingers extending from the moveable plate, between the
electrodes, the moveable plate and electrode forming a motion sensor.

19. A method of fabricating a device comprising: forming a moveable plate
over a substrate; forming an energy harvesting coil in the moveable
plate; and forming electrodes around the moveable plate, the electrodes
adapted to sense motion of the moveable plate.

20. The method according to claim 19, further comprising: forming at
least one of springs or hinges to attach the moveable plate to the
substrate; and forming wiring connecting the energy-harvesting coil to at
least one of bond pads or a control circuit formed on the substrate.

Description:

BACKGROUND

[0001] Sensors are sometimes placed in locations where there is no power
supply or the power supply is limited by, for example, the battery life
or size. Some Micro-electromechanical systems (MEMS) sensors have a power
consumption great enough to impact battery life in many applications in
which the MEMS sensors would be useful. Such MEMS sensors include sensors
for detecting position, velocity, acceleration or magnetic fields.
Applications for such MEMS sensors include, for example, navigation for
smart phones.

[0002] Kinetic electromagnetic-induction MEMS energy-harvesters convert
mechanical energy into electrical energy by converting mechanical motion,
such as deformation, displacement, velocity, and/or acceleration, of a
portion or all of an energy-harvester into electrical current and
voltage. The electrical energy is used to power an attached device.

DESCRIPTION OF THE DRAWINGS

[0003] One or more embodiments are illustrated by way of example, and not
by limitation, in the figures of the accompanying drawings, wherein
elements having the same reference numeral designations represent like
elements throughout and wherein:

[0004] FIG. 1 is a device comprising a Lorentz force magnetic sensor and
integrated energy-harvesting functionality according to an embodiment;

[0005]FIG. 2 is a device comprising a motion sensor and integrated
energy-harvester according to an embodiment;

[0006] FIGS. 3A-3K are cross-sectional views of the device of FIG. 1 or
the device of FIG. 2 during various stages of manufacturing according to
an embodiment;

[0007] FIGS. 4A-4K are cross-sectional views of the device of FIG. 1 or
the device of FIG. 2 during various stages of manufacturing according to
another embodiment; and

[0008]FIG. 5 is a high-level functional block diagram of a sensor system
including the device of FIG. 1 or the device of FIG. 2 according to an
embodiment.

DETAILED DESCRIPTION

[0009] FIG. 1 is a device 100 comprising a Lorentz force magnetic sensor
101 and an integrated energy-harvester 102 formed within an area of the
Lorentz force magnetic sensor according to an embodiment. The device 100
comprises a substrate 105 with a raised structure 110 and bond pads 112
formed on a surface of the substrate. The raised structure 110 comprises
a rectangular-shaped outer portion 115 affixed to the substrate 105 and a
rectangular-shaped inner portion 120 free from the substrate but
connected to and formed within the outer portion 115. The inner portion
120 is separated from the outer portion 115 by a pair of slots 122 formed
in the raised structure 110 and around a periphery of the inner portion.
The Lorentz force magnetic sensor 101 comprises the inner portion 120,
two elastic connections 125, a first wire loop 130 and electrodes 132.
The two elastic connections 125 attach the outer portion 115 to the inner
portion 120. The elastic connections 125 are formed in the middle of
opposite sides of the inner portion 120, allowing the inner portion to
rotate about an axis A defined by the elastic connections 125.

[0010] In at least some embodiments, there are greater or fewer numbers of
elastic connections connecting the inner and outer portions. In at least
some embodiments, the raised structure 110 and the inner and outer
portions 120, 115 comprise different shapes, e.g., square, polygonal,
ellipsoid, circular, etc. In at least some embodiments, the inner portion
120 is different shaped from the outer portion 115.

[0011] The first wire loop 130 is formed along an outer edge of the inner
portion 120. Portions near the two ends of the wire loop 130 are formed
on one of the elastic connections 125 so that the wire loop ends are
formed on the outer portion 115. On the outer portion 115, the two ends
of the first wire loop 130 are connected to pads 135. The pads 135 are
connected (not shown for clarity) by vias formed through the raised
structure 110 and wiring formed under the raised structure to bond pads
112 formed on the substrate 105. The electrodes 132 (positioning
indicated by dashed lines) are formed on the substrate 105 underneath the
inner portion 120. The raised structure 110 also comprises the integrated
energy-harvester 102. The integrated energy-harvester 102 comprises a
second wire loop 145 formed in a spiral loop arrangement inside the first
wire loop 130 and a connection wire 150. In at least some embodiments,
second wire loop 145 comprises a spiral loop having a circular,
rectangular, or other shape. A portion of the second wire loop 145 near
to a first end of the second wire loop is formed on one of the elastic
connections 125 so that the first end of the second wire loop is formed
on the outer portion 115. A second end of the second wire loop 145 is at
the center of the inner portion 120 and connected to a first end of the
connection wire 150. The connection wire 150 is formed to cross over the
over spiral loops of the second wire loop 145 but does not electrically
connect to the spiral loops at the crossing points. A portion of the
connection wire 150 near to the second end of the connection wire is
formed on the other of the elastic connections 125 so that the second end
of the connection wire is formed on the outer portion 115. The second end
of the connection wire 150 is connected by a via formed through the
raised structure 110 and wiring formed the under the raised structure to
bond pads 112. In some embodiments, one elastic connection 125 is used to
connect the inner portion 120 with the outer portion 115. In other
embodiments, more than two elastic connections 125 are used to connect
the inner portion 120 with the outer portion 150. In some embodiments,
the vias formed in the raised structure 110 and the wiring formed under
the raised structure connect (not shown for clarity) the Lorentz force
magnetic sensor 101 and the integrated energy-harvester 102 to a circuit
formed on the substrate 105.

[0012] In operation, an alternating current supplied by a control circuit
and passed around the first wire loop 130 causes a force on the wire
proportional to a magnetic field in the vicinity of the first wire loop.
In at least some embodiments, the control circuit is formed on the
substrate 105. A component of the magnetic field in a direction in the
plane of the inner portion 120 and perpendicular to the axis A causes a
net force on the first wire loop 130 that causes the inner portion 120 to
rotate about the axis A. Because the current passed around the first wire
loop 130 alternates, the inner portion 120 oscillates back and forth
around the axis A. Components of the magnetic field in other directions
do not cause movement of the inner portion 120. The motion of the inner
portion is detected capacitively as the inner portion moves by the
electrodes 132. Thus, the Lorentz force magnetic sensor 100 measures one
component of the magnetic field. Additional similar sensors positioned at
different angles enable other components of the magnetic field to be
sensed. The Lorentz force magnetic sensor 101 detects, for example, the
magnetic field of the Earth.

[0013] The elastic connections 125 also act as return springs causing the
position of the inner portion 120 to return to the plane of the outer
portion 115 if no force is applied to the inner portion e.g., via first
wire loop 130. The elasticity of the elastic connections 125 and the mass
of the inner portion 120 cause the rotation mode of the inner portion to
have a resonant frequency corresponding to the elasticity of the elastic
connections 125 and a mass of the inner portion. If the alternating
current frequency is selected to match the resonant frequency of the
inner portion 120, the displacement of the inner portion due to the
magnetic field is increased by a quality factor Q of the mechanical
system formed by the mass of the inner portion 120 and elastic
connections 125. Further, the response time to a change in the magnetic
field increases by the quality factor Q.

[0014] The magnetic field impinging on the first wire loop 130 also passes
through the spiral of the second wire loop 145 of the integrated
energy-harvester 102. Changes in the magnetic flux enclosed by the area
formed by the second loop 145 induce a voltage across the ends of the
second loop. The voltage induced is proportional to the rate of change of
the magnetic field coupled to the second loop 145. Thus, movement of
device 100 into or out of a magnetic field, rotation of device 100 in a
magnetic field or an alternating magnetic field passing through the
sensor generated by, for example, power lines carrying alternating
current causes voltage generation across the ends of the second loop 145.

[0015] Further, if the inner portion 120 moves due to the alternating
current in the first wire loop 130 and an external magnetic field, a
voltage will be induced across the second wire loop 145 by the rotation
of the inner portion about the magnetic field.

[0016] Independent of how the voltage across the second wire loop 145 is
generated, the voltage generates a current in the second wire loop. A
power proportional to the product of the voltage across the second wire
loop 145 and the current through the second wire loop is extracted from
the second wire loop and the power provided by the integrated
energy-harvester 102 used to supplement the power for driving the Lorentz
force magnetic sensor 101. In some embodiments, the power extracted is
sufficient to drive the device 100.

[0017] In some embodiments, the power is extracted from the second wire
loop 145 of the integrated energy-harvester 102 at the same time as a
measurement of the magnetic field passing through the Lorentz force
magnetic sensor 101. In other embodiments, the power is extracted from
the second wire loop 145 of the integrated energy-harvester 102 between
measurements of the magnetic field passing through the Lorentz force
magnetic sensor 101.

[0018]FIG. 2 is a device 200 comprising a motion sensor 201 and an
integrated energy-harvester 202 formed within an area of the motion
sensor according to an embodiment. The device 200 comprises a substrate
205 with raised structures and with bond pads 207 formed on a surface of
the substrate 205. The raised structures comprise an outer portion 210,
anchor portions 215 fixed to the substrate 205, a free portion 220 free
from the substrate and two sets of sense electrodes 222, 224.

[0019] The motion sensor 201 comprises the anchor portions 215 the free
portion 220, the sense electrodes 222, 224, and hairpin springs 225. The
free portion 220 is attached to the anchor portions 215 by the hairpin
springs 225 at corresponding top and bottom edges of the free portion
with respect to the page. The hairpin springs 225 allow the free portion
to move relative to the outer portion 210 in a direction along an axis B
defined by the middle of the two sides of the free portion 220 attached
to the hairpin springs 225. The free portion 220 is also free to move
toward or away from the substrate 205, i.e., into or out of the page.

[0020] The free portion 220 comprises fingers 229 that extend away from
the sides of the free portion not attached to the hairpin springs 225.
The sense electrodes 222, 224 are formed on either side of the fingers
229, and are attached (not shown for clarity) to the bond pads 207 by
vias formed through the raised structures 210, 215, 220, 222, 224 and
wiring formed under the raised structures.

[0021] In some embodiments, the hairpin springs 225 are replaced by other
elastic structures compatible with embodiments of the disclosure that
allow the free portion 220 to move relative to the outer portion 210 in a
direction along an axis B.

[0022] The device 200 further comprises the integrated energy-harvester
202 formed by a wire loop 230, a portion of a first connection wire 235
and a portion of a second connection wire 240 formed on the free portion
220. The wire loop 230 is formed in a spiral arrangement. A first end of
the wire loop 230 is connected to the first connection wire 235 formed on
one of the hairpin springs 225 and connecting across from the free
portion 220 to one of the adjacent anchor portions 215. A second end of
the wire loop 230 is at the center of the free portion 220 and connected
to a first end of the second connection wire 240. The second connection
wire 240 crosses over the spirals of the wire loop 230 but is not
electrically connected thereto. The second connection wire 240 is formed
on the other of the hairpin springs 225 and connects across from the free
portion 220 to the other anchor portion 225. The second end of the first
and second connection wires 235, 240 are connected (not shown for
clarity) via vias formed through the anchor points 225 and wiring formed
under raised structures 210, 215, 220, 222, 224 to the bond pads 207.

[0023] In operation, the free portion 220 is displaced relative to the
substrate 205 when the substrate is accelerated. The mass of the free
portion 220 acts as a proof mass. The proof mass is the mass which is
accelerated by the deformation of the hairpin springs 225 if the
substrate 205 is accelerated. The displacement relative to the substrate
of the proof mass is determined by the acceleration, the elasticity of
the hairpin springs 225, and the proof mass of the free portion 220. The
displacement of the free portion 220 relative to the substrate is
detected by the electrodes 222, 224 by electrostatic sensing. Thus, the
acceleration of the motion sensor 201 is measured. In some embodiments,
motion of the free portion 220 toward or away from the substrate is
detected by optional electrodes formed on the substrate 205 underneath
the free portion. Additional similar sensors positioned at different
angles, enable other components of the acceleration to be measured.

[0024] A magnetic field impinging on the device 200 passes through the
spiral of the wire loop 230. The magnetic field can be produced by an
optional permanent magnet 255. Changes in the total magnetic field
passing through the area formed by the wire loop 230 cause a voltage to
be induced across the ends of the loop. The voltage induced is
proportional to the rate of change of the magnetic field. Thus, movement
into or out of a magnetic field, rotation in a magnetic field or an
alternating magnetic field generated by, for example, power lines
carrying alternating current cause a voltage to be generated across the
wire loop 230.

[0025] Further, motion of the free portion 220 relative to the substrate
205 due to acceleration of the device 200 induces a voltage across the
wire loop 230 if the motion of the wire loop causes a change in the
magnetic flux enclosed by the wire loop. In some embodiments, the
permanent magnet 255 is integrated into the device 200 or placed next to
the device 200 to produce a suitable magnetic field which the wire loop
230 moves through when accelerated.

[0026] Independent of how the voltage across the wire loop 230 of the
integrated energy-harvester 202 is generated the voltage is used to
generate a current in the second wire loop. A power proportional to the
product of the voltage across the second wire loop 230 and the current
through the second wire loop is extracted from the second wire loop of
the integrated energy-harvester 202 and used to supplement the power for
driving the device 200. In some embodiments, the power extracted is
sufficient to drive the device 200.

[0027] In some embodiments, the power is extracted from the second wire
loop 230 at the same time as a measurement of the acceleration of the
motion sensor 201. In other embodiments, the power is extracted from the
second wire loop 230 between measurements of the acceleration of the
motion sensor 201.

[0028] In at least one embodiment, both of the devices 100, 200 described
above are fabricated using a MEMS process.

[0029] FIGS. 3A-3K are cross-sectional views of the device 100 or the
device 200 during various stage of manufacturing according to an
embodiment.

[0030] In FIG. 3A, a metal layer 305 is deposited on a substrate 310. The
metal layer is fabricated using any process compatible with embodiments
of the disclosure, for example, evaporation, sputtering, chemical vapor
deposition or plating. The metal layer 305 comprises, for example, one or
more of copper, gold, silver, nickel, titanium, tantalum, chromium,
titanium nitrate, aluminum or alloys thereof.

[0031] In FIG. 3B, the metal layer 305 is patterned using any process
compatible with embodiments of the disclosure. The patterning process
includes, for example, coating with photoresist, exposure of the
photoresist through a mask and developing the photoresist. Subsequently,
metal exposed through the photoresist is etched using, for example, a wet
etching process, ion milling, reactive ion milling or plasma etching. In
other embodiments, the metal layer 305 is formed and patterned by a
lift-off process.

[0032] The patterned metal layer 305 forms the electrodes 132 and wiring
from the vias to the bond pads 112 of the device 100 or the wiring,
optional electrodes on the substrate and bond pads 207 of the device 200.

[0033] In FIG. 3c, an oxide layer 315 is formed over the metal layer 310.
The oxide layer 315 is formed by, for example, chemical vapor deposition,
sputtering or plasma enhanced chemical vapor deposition. The oxide layer
315 is patterned to form depressions 320 using processes similar to one
or more of the photoresist process and etching process used to pattern
layer 305.

[0034] In FIG. 3D, the oxide layer 315 is further patterned to form
pillars 325 of differing heights using processes similar to one or more
of the photoresist process and etching process used to pattern layer 305.

[0035] In FIG. 3E, a highly doped silicon wafer 330 is fusion bonded to
the oxide layer 315. The highly doped silicon wafer 330 is ground down to
a suitable thickness, for example, 30 μm. The free portion 220 of
device 200 and the inner portion 120 of device 100 are ultimately formed
from the ground highly doped silicon wafer 330. Because the highly doped
silicon wafer 330 is quite thick compared with the thickness of a layer
of polysilicon that it is reasonable to deposit, the free portion 220 of
motion sensor 201 has a large mass compared with a layer of deposited
polysilicon. Thus, the proof mass formed by the free portion 220 is more
massive and the motion sensor more sensitive than a sensor formed by a
layer of deposited polysilicon.

[0036] In FIG. 3F, the ground silicon wafer 330 is patterned and etched in
one or more etch processes to form through-holes 335, trenches 340 and
pillars 345. The patterning and etching processes similar to one or more
of the photoresist process and etching process used to pattern layer 305.

[0037] In FIG. 3G, the through-holes 335 and trenches 340 are filled with
a electrical insulating materials, for example silicon dioxide, and
conducting material 360, for example, titanium nitrate and tungsten
using, for example, a chemical vapor deposition and polishing process.
The material in the trenches forms the first and second wire loops 130,
145 of the device 100 and the wire loop 230 of the device 200 and the
vias connecting the first and second wire loops 130, 145 and the wire
loop 230 to the bond pads 112, 207.

[0038] In FIG. 3H, insulation material 365, for example, silicon dioxide
or silicon nitride is formed over the ground silicon wafer and the
conducting material 360. Over the patterned insulation material 365,
wiring 370 is formed. The wiring 370 corresponds to connection wire 150
of the device 100 and the first and second connection wires 235, 240 of
the device 200.

[0039] In FIG. 3I, slots 375 are etched through the ground silicon wafer
330. The slots 375 delineate the inner portion 120 and the elastic
connections 125 of the device 100 and the hairpin springs 225, anchor
portions 215, free portion 220 and electrodes 222, 224 of the device 200.

[0040] In FIG. 3J, a capping wafer 380 is bonded to portions of the metal
305 that form a bonding ring around the device 100 and the device 200.

[0041] In FIG. 3K, an optional hard magnetic layer 385 is coated on the
backside of the substrate 310 and a top surface of the capping wafer 380.
The optional hard magnetic layer 385 is magnetized so that the field
generated by the permanent magnet formed by the magnetized magnetic layer
385 causes current generation in the second wire loop 145 or the wire
loop 230 if the second wire loop 145 or the wire loop 230 moves relative
to the magnetic field.

[0042] FIGS. 4A-4L are cross-sectional views of the device 100 or the
device 200 at various stages of manufacturing according to another
embodiment.

[0043] In FIG. 4A, insulating layers 405 are deposited on a top surface
and a bottom surface of a substrate 410. Insulating layers 405 are formed
from, for example, silicon oxide or silicon nitride by, for example,
chemical vapor deposition, sputtering or in the case of silicon oxide by
thermal growth. Top and bottom metal layers 407a/407b are formed on the
insulating layers 405. The metal layer 407 is fabricated using any
process compatible with embodiments of the disclosure, for example,
evaporation, sputtering, chemical vapor deposition or plating. The metal
layers 407a/407b comprise, for example, one or more of copper, gold,
silver, nickel, titanium, tantalum, chromium, titanium nitrate, aluminum
or alloys thereof.

[0044] In FIG. 4B, top metal layer 407a is patterned and etched using
processes similar to one or more of the photoresist process and etching
process used to pattern layer 305.

[0045] In other embodiments, the metal layer 407a is formed and patterned
by a lift-off process. In other embodiments, metal layers 407a and 407b
are polysilicon.

[0046] The patterned top metal layer 407a forms the electrodes 132 and
wiring from the vias to the bond pads 112 of the device 100 or the
wiring, optional electrodes on the substrate and bond pads 207 of the
device 200.

[0047] In FIG. 4c, an oxide layer 415 is formed over the top metal layer
407a. The oxide layer 415 is formed by, for example, chemical vapor
deposition, sputtering or plasma enhanced chemical vapor deposition.

[0048] In FIG. 4D, polysilicon layer 420 is deposited on the oxide layer
415. The free portion 220 of the device 200 and the inner portion 120 of
device 100 are ultimately formed from the polysilicon layer 420.

[0049] In FIG. 4E, the polysilicon layer 420 is patterned and etched in
one or more etch processes to form through-holes 425 and trenches 430
using processes similar to one or more of the photoresist process and
etching process used to pattern layer 305.

[0050] In FIG. 4F, the through-holes 425 and trenches 430 are filled with
a conducting material 435, for example, titanium nitrate and tungsten
using, for example, a chemical vapor deposition and polishing process.
The material in the trenches forms the first and second wire loops 130,
145 of the device 100 and the wire loop 230 of the device 200 and the
vias connecting the first and second wire loops 130, 145 and the wire
loop 230 to the bond pads 112, 207.

[0051] In embodiments in which 407a and 407b are polysilicon, the oxide
layer 415 is deposited and patterned to form the through-holes 425.
Polysilicon is deposited over the oxide layer 415 to form a continuous
polysilicon layer 420. The continuous polysilicon layer is subsequently
patterned to form trenches 430. The conductive material 435 are formed in
the trenches 430.

[0052] In FIG. 4G, insulation material 440, for example, silicon dioxide
or silicon nitride is formed over the polysilicon layer 420 and the
conducting material 435. The insulation material 440 is patterned and
etched using processes similar to one or more of the photoresist process
and etching process used to pattern layer 305. Over the patterned
insulation material 440, wiring 445 is formed. The wiring 445 corresponds
to connection wire 150 of the device 100 and the first and second
connection wires 235, 240 of the device 200.

[0053] In FIG. 4H, slots 450 are etched through the polysilicon layer 420.
The slots 450 delineate the inner portion 120 and the elastic connections
125 of the device 100 and the hairpin springs 225, anchor portions 215,
free portion 220 and electrodes 222, 224 of the device 200.

[0054] In FIG. 4I, portions 455 of the oxide layer 415 are etched via the
slots 450 by, for example, an HF vapor etch or a buffered HF wet etch.

[0055] In FIG. 4J, a bonding ring 460 is formed and patterned on top of
polysilicon layer 420 using processes similar to one or more of the
photoresist process and etching process used to pattern layer 305.

[0056] In other embodiments, the bonding ring 460 is formed and patterned
by lift-off process. In some embodiments, the bonding ring 460 is formed
and patterned at the same time as forming wiring 445 or immediately after
formation of wiring 445.

[0057] In FIG. 4K, a capping wafer 465 is bonded to the bonding ring 460
around the device 100 or the device 200.

[0058] An optional hard magnetic layer 385 (FIG. 3K) is coated on the
backside of the substrate 410 over bottom metal layer 407b and a top
surface of the capping wafer 465. The optional hard magnetic layer 385 is
magnetized so that the field generated by the permanent magnet formed by
the magnetized magnetic layer 385 causes current generation in the second
wire loop 145 or the wire loop 230 if the second wire loop 145 or the
wire loop 230 moves relative to the magnetic field.

[0059] In both of the processes depicted in FIGS. 3A-3K and 4A-4K the
capping wafer 380, 465 and the bonding rings form a seal that protects
the device 100 and the device 200 from the environment.

[0060]FIG. 5 is a functional diagram of a sensor system 500 according to
an embodiment. Sensor system 500 comprises a MEMS sensor 505, a
controller 510, signal processing electronics 515 and an optional
permanent magnet 520. The MEMS sensor 505 comprises one or more MEMS
sensors with energy-harvester 100, 200 described above. The controller
510 controls the MEMS sensor 505 and collects energy from the
energy-harvester, redistributing the collected energy to the MEMS sensor
505 and the signal processing electronics 515, thus reducing the power
consumption of the sensor system. In some embodiments, the MEMS sensor
505 is on the same substrate as a substrate on which the controller 510
and signal processing electronics 515 is formed. In some embodiments, the
controller 510 and signal processing electronics 515 are formed on the
substrate beneath the MEMS sensor 505. In some embodiments, the
controller 510 and signal processing electronics 515 are formed on the
same substrate as the MEMS sensor 505 but in a different portion of the
substrate, either at the same side or a different side from the side
where the sensor is formed. In other embodiments, the controller 510 and
signal processing electronics 515 for the sensor system 500 are formed on
a separate substrate and wire bonded or die bonded to the substrate with
the MEMS sensor 505. The optional permanent magnet 520 produces a
magnetic field for the energy-harvester of the MEMS sensor 505.

[0061] According to some embodiments, a sensor comprises a substrate, a
sensor element and an energy-harvesting device. The sensor element
comprises a suspended plate, and the suspended plate is moveable with
respect to the substrate. The energy-harvesting device is formed on the
suspended plate of the sensor element.

[0062] According to some embodiments, a sensor system comprises a moveable
plate, an energy-harvesting device and a controller. The moveable plate
is moveable with respect to the sensor system and adapted to move
responsive to an environmental variable. The energy-harvesting device is
formed on the moveable plate. The controller adapted to power the sensor
system using at least energy harvested from the energy-harvesting device.

[0063] According to some embodiments, a method of fabricating a sensor
comprises forming a moveable plate, forming an energy harvesting coil and
forming electrodes around the moveable plate. The moveable plate formed
over a substrate. The energy-harvesting coil is formed in the moveable
plate. The electrodes are formed around the moveable plate, and the
electrodes are adapted to sense motion of the moveable plate.

[0064] It will be readily seen by one of ordinary skill in the art that
the disclosed embodiments fulfill one or more of the advantages set forth
above. After reading the foregoing specification, one of ordinary skill
will be able to affect various changes, substitutions of equivalents and
various other embodiments as broadly disclosed herein. It is therefore
intended that the protection granted hereon be limited only by the
definition contained in the appended claims and equivalents thereof.